The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Within the motor vehicle automatic transmission art, the dual clutch transmission (DCT) is a relative newcomer. A typical dual clutch transmission configuration includes a pair of mutually exclusively operating input clutches which drive a pair of layshafts or countershafts disposed on opposite sides of an output shaft. One of each of a plurality of pairs of constantly meshing gears which define the various forward gear ratios is freely rotatably disposed on one of the layshafts and the other of each pair of gears is coupled to the output shaft. A plurality of dog clutches selectively couple one of the gears to the layshaft to achieve a forward gear ratio. After the dog clutch is engaged, the input clutch associated with the active layshaft is engaged.
Dual clutch transmissions are known for their sporty, performance oriented shift characteristics. They typically exhibit good fuel economy due to good gear mesh efficiency and ratio selection flexibility in design. The dog clutches have low spin losses which also contributes to overall operating efficiency.
However, dual clutch transmissions have several unique design considerations. For example, because of the torque throughput during launch and the heat that can be generated during slip, the input clutches must be of a relatively large size. The size requirement applies as well to the cooling system which must be able to dissipate relatively large quantities of heat. Finally, because such transmissions typically have many sets of axially aligned gears, their overall length may be problematic in some platform configurations.
The present invention is directed not only to providing a dual clutch automatic transmission have reduced axial length but also to such a transmission for incorporation into a hybrid powertrain.